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    <p>You're not really making a 2D array, you're making an array of pointers that point to arrays of pixels. That means your first <code>calloc</code> call should allocate enough space for pointers, not for pixels:</p> <pre><code>pixel **pixelvalue = calloc(imginformation.width, sizeof(pixel *)); </code></pre> <p>You didn't tag your question with a language, but assuming it's C (based on your <code>typedef</code>, which wouldn't be necessary in C++), you shouldn't be casting the return values of <code>calloc()</code>. Doing so can hide bugs with <code>#include</code> that could come back to bite you down the road.</p> <p><strong>Edit:</strong></p> <p>You asked a couple of follow-up questions. The first has been answered pretty well by several other answers, I think, but I'll try to summarize. The way you're doing the allocation, you are first going to allocate an array of pointers - each of those pointers is going to point to one row of your array. The rows themselves then need to be allocated - space for each <code>pixel</code> object goes there, and the pointers to the rows are stored in the first array of pointers.</p> <p>Your second question, bout the return value from <code>calloc()</code> is pretty straightforward. If you cast the return value, you can hide implicit declaration bugs from yourself. Since the return type of <code>calloc</code> is <code>void *</code>, if you do something like:</p> <pre><code>my_ptr = calloc(1, 2); </code></pre> <p>Everything works nicely. Now imagine that you didn't include <code>stdlib.h</code>, and therefore had no prototype of <code>calloc()</code> in your translation unit. That would lead the compiler to assume the signature of <code>calloc()</code> to be <code>int calloc(int, int)</code>, which isn't true. The same line of code above would throw you a warning about assuming a default signature for that function. Using a typecast like you have in your code will mask that warning and you might never know you were missing that <code>#include</code> line.</p>
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    1. USCarl Norum
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    1. COHi, thanks your solution works fine. Now I have a few understanding problems, see me Edit. Thanks.
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    2. CO@Taz - I'll edit to address your modifications momentarily.
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